Quiero usar la función FEC. Cuando conecto los dos pares de puertos de los dos conmutadores con dos cables al mismo tiempo, Encuentro que cada switch es siempre un puerto normal y el otro puerto muestra una luz roja. ¿El puerto del switch está defectuoso??

In general, this situation switch is normal, because the two switches are connected by two ports, so the switch thinks that there is LOOP, it automatically disconnects one of them and drops the corresponding port Down (the port showing the red light). The solution is: turn on the function of Spanning-tree (it is turned on by default), and let the switch know that these two ports are functions of FEC, which is logically a port.